1. Field of the Invention
The present invention relates to a cup attaching apparatus for attaching a cup as a processing jig used for processing an eyeglass lens to a surface of the lens.
2. Description of Related Art
As a cup attaching apparatus, there is known an apparatus comprising an illumination optical system for projecting illumination light to a lens from a front surface side of the lens, a measurement index of a predetermined pattern and a screen placed at a back surface side of the lens, and an imaging optical system including an imaging device for imaging an image of the measurement index and an image of the lens projected on the screen. This apparatus is arranged to detect an optical center and a cylinder axis angle of the lens by processing an image signal from the imaging device, and determine an attaching position of the cup based on a detection result thereof (e.g., see U.S. Pat. No. 6,798,501B1 (JP2000-79545A)). Such apparatus is configured so that, for a unifocal lens or the like marked with a mark point on a lens surface (a lens front or back surface), an image of the mark point is projected onto the screen; for a bifocal lens, an image of a small lens portion is projected onto the screen; and for a progressive focal lens, an image of a mark printed on a lens surface is projected onto the screen. The image projected onto the screen is imaged by the imaging device to determine the attaching position of the cup.
Further, another apparatus has also been proposed, comprising an illumination optical system for projecting diffused illumination light onto a lens through a diffusion plate from a back surface side of the lens, and an optical system for observing or imaging, from a front surface side of the lens, an image of the lens illuminated by the diffused illumination light (see for example JP3(1991)-113415). Further, another apparatus has also been proposed, including an illumination optical system for projecting illumination light to a lens from a front surface side of the lens, a retroreflection member placed at a back surface side of the lens to reflect the light passing through the lens back to its incoming direction, and an imaging optical system for imaging, from the front surface side of the lens, an image of the lens illuminated by the light reflected by the retroreflection member, so that a hidden mark, a progressive mark, or the like of a progressive focal lens can be imaged (see for example, EP1739472A1 (JP2005-316436)).
Such an apparatus using the screen would have problems in detection accuracy because the measurement index image is blurred due to roughness of the screen, and the mark point image, the small lens portion image of the bifocal lens, the mark image of the progressive focal lens, and others are projected in blurred and distorted states onto the screen due to refractive powers of the lenses.
Moreover, the apparatus arranged to illuminate the lens by the diffused illumination light from the back surface side of the lens could not easily detect (determine) an outer edge of the lens, a small lens portion edge of the bifocal lens, and others.
In the apparatus disclosed in EP 1739472A1 (JP2005-316436A), the optical system for detecting an optical center of the lens and others forms an optical path different from that of the optical system for imaging the lens image, resulting in a complicated apparatus configuration and a large sized apparatus.